It won't suddenly gets expensive, but it will gradually go
higher in years.  For example, Gundam Wing has been showing
on Cartoon Networks for quite a while, the prices of the
cels for this show actually is around the same range before
it shows on TV, may be certain characters are a bit more
expensive than before.  But in the few years, I expect the
prices will go higher as it established its brand name,
re-run the shows on network station, sell the videos to more
big stores...etc.  Looking at Sailor Moon, the cel prices
in the early years are cheap, but after a few years, the
prices have all went higher because there're more people
have watched SM than years ago.  
With CCS showing on Kids WB, this certainly helps to 
increase its popularity even quicker, just liked what they
did with Pokemon.  There're liked 70 CCS episodes 
and the anime studio are releasing only part of the cels.  
There're plenty of CCS cels for everyone to buy now, even
with the US showing it soon, the studio still have tons
of cels to release them gradually, so I expect the cel
prices will be fair in the short run.  But in the long run,
certain characters or scenes of the cels will be definitely
go higher.